The present invention relates to a method of producing a continuous-thread disk element from which to form composite materials.
In British Patent Application n. 2 168 032 filed on Oct. 2, 1985, composite materials are produced by forming a number of disks, each obtained by winding a continuous reinforcing thread about an axis to form a flat coil; stacking the disks with a matrix spacer sheet between each disk and the next; and axially compacting the stack so formed to obtain a matrix in which the various coils of reinforcing thread are embedded.
The physical characteristics of the composite materials obtained as described above mainly depend on the distribution of the reinforcing threads inside the matrix; and homogeneous distribution of the threads depends on the extent to which the turns in each disk are equally spaced, and the extent to which the freedom of movement of the various turns is limited, especially during compression.
In British Patent Application n. 2 168 032, the turns in each disk are spaced and locked with respect to one another by interposing between each turn and the next a continuous spacer bead, which is wound simultaneously with the reinforcing thread about the axis of the disk, and is connected to the reinforcing thread by means of a binding material, preferably an acrylic resin.
In the above method, the mutual position of the turns of reinforcing thread, i.e. the distance between one turn and the next, depends on the geometric characteristics of the spacer bead, which must be sized in each case according to the desired distribution of the reinforcing thread inside the matrix, and must be made of different materials, depending on the matrix involved, so that production time and cost are obviously fairly high.
Moreover, the above method is also unsatisfactory by failing to allow a reduction, below a relatively high minimum threshold value, in the spacing or distance between the turns in each disk, and in the thickness of the reinforcing thread disks themselves. In fact, the materials and known techniques normally used to form the beads impose a minimum transverse dimension of the beads, which is normally always greater than the minimum transverse dimension of the reinforcing threads, so that the above known method fails to provide for producing composite materials with any reinforcing thread distribution or density.